Sci-Ence! Justice Leak!

A revised and improved version of this essay is in my book Sci-Ence! Justice Leak! – hardback, paperback, PDF Kindle (US), Kindle (UK), all other ebook formats

One possible path of the positions of three particles, from Julian Barbour's The End Of Time

What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know. – Saint Augustine

This post comes with a health warning – I am talking here about quantum physics. There is nothing more likely to produce wrongheaded drivel than this, of the “did you hear, right, there’s this cat and it’s in a box, and if you look into the box you go into another universe?” variety. Even most professional quantum physicists, once they start talking about what the equations actually *mean*, tend to start saying things which every other physicist will find ridiculous and unscientific.

So with that in mind, please assume that everything I say here is wrong. What I’m going to talk about here isn’t the truth, but rather a set of ideas put forward by a group of physicists including David Deutsch, Max Tegmark and Julian Barbour, as I understand them based on their explanations. These physicists are all people who are respected in their fields, but who are definitely in the minority as far as their explanations of reality go, so I’m not talking here about what reality ‘really is’.

But I *do* think that not only are these ideas interesting in themselves, they’re also an influence on the comics of Grant Morrison, which I’ve been talking about and will be talking about in this series. I suspect the idea of Hypertime has its origins in these ideas, which are expressed most fully in Barbour’s book The End Of Time, and most clearly in Deutsch’s The Fabric Of Reality. I’m going to oversimplify hugely here, but I’ll give a bibliography at the end of books which only oversimplify quite a lot…

One of the basic problems in physics over the last century or so has been an experiment that anyone can do at home, at least in its basics. If you shine a point source of light through a double slit onto a screen, you see fringes of light and darkness – interference patterns. These patterns are characteristic of things that exist as waves, like sound, but we know from other experiments that light comes in particles, which we call photons.

Now, when a lot of light is being shone through the slits, the explanation seems simple enough – all the photons travelling through the slits are interfering with each other – bouncing off the photons coming through the other slit, if you like – which is why we get the pattern. But this pattern also happens if we send *one photon at a time* through the slits – it builds up into exactly the same pattern as when we send lots through at once.

So how can a photon interfere with itself (no sniggering at the back there)?

Well, we have an equation – the Schrodinger equation – which lets us predict very accurately (but statistically) how many photons will land where. It doesn’t tell us where any given photon will land, but it does say that given x number of photons travelling through the slits, so many will land here, and so many there. The problem is trying to explain what this equation *means*.

There are several different explanations of it, but the two most popular are the Copenhagen Interpretation and the Many-Worlds hypothesis. The Copenhagen interpretation essentially says that when you send a photon through a bit of card with two slits, it sort of ‘smears out’ in space and time, and is everywhere it could possibly be until we look at it. When we look at it, it decides to be in just one place, and it’s never been in any of the others – it’s retrospectively only taken one of the paths it smeared out across.

The many worlds interpretation, on the other hand, says that in fact there are loads of different photons – as many as there are different paths the photon could take – but that we can only see one, the others being in separate universes. But the photons still bounce off each other, causing the interference patterns.

Now, as far as the maths goes, these two give exactly the same results – at present we have no way at all of distinguishing between them, so choosing between them is mostly a matter of aesthetics – whether you think it’s neater to say “if we look at something, it’s magically in just one place and we don’t know why” or “there are a near-infinity of actually-existing universes out there, most of which only differ by things like the position of one electron in a star fifteen galaxies away”. Neither of these seem especially neat or preferable to me…

But some of the physicists who favour the idea of a multiverse go further. They point out that, looking at these equations, there’s nothing to differ the past and the future from other universes. What we see as moving forward through time could just as easily be explained as a line ‘drawn’ through ‘neighbouring’ universes – those which are almost identical, except for small movements which are in line with the laws of physics.

So instead of time passing in a single universe, our experience of time could equally be put down to a contour that can be drawn through a near-infinite number of points in a multi-dimensional configuration space. That line wouldn’t have to go in any particular direction, so long as it was a continuous line – the laws of physics are (with a couple of possibly-explicable exceptions) time-reversible anyway.

So why do we have a sense of time going in one direction? Well, there are more ways of arranging things in a disordered manner than in an ordered manner, which means that there are more disordered universes than there are ordered ones. So if you draw a line from one universe (with enough order in it to have human beings who can think and write blog posts and so on) to another one very close to it (and therefore very similar), the chances are that the one next to it will be slightly less ordered. And the next one in the line will be less ordered again.

From this, then, we get a sense of direction – at any point, things are going to act in ways consistent with the laws of physics (because the universes next to us are those where particles have moved in ways it is possible for them to move), but overall disorder – entropy – is going to increase. So if we hit a cup with a hammer, we see it smash, but if we hit smashed crockery with a hammer, it doesn’t turn into a cup – because there are lots of ways to arrange those molecules into smashed crockery, but only one to arrange it into a cup.

But just because we’re experiencing one line, that doesn’t make it the ‘true’ line. There are a near-infinite number of ways to get to any universe, and a near-infinite number of directions it can go. That means there are a practically infinite number of those lines, all crossing each other. Every line that’s consistent with the laws of physics is a ‘universe’ just as real as our own – there is one ‘universe’ where every instant in its history up until the point at which I hit the next comma in this sentence is different from the instants in this universe, and where every instant going forward is different, but which overlapped with this universe at precisely that point and only that point. In fact (assuming this interpretation is true) there are an infinite number of such universes.

Now, doesn’t that sound to you like

Take a glass sphere studded all over with holes, and then drive a long stick right through the middle of it, passing exactly through the center of the volume. That’s the base DC timeline. Jab another stick through right next to it, but at a different angle, so that they’re touching at one point. That’s an Elseworlds story. Another stick, this one rippled, placed close in so that it touches the first stick at two or three points. That’s the base Marvel timeline. Perhaps others follow the line of the DC stick for a while before diverging, a slow diagonal collision along it before peeling off. This sphere contains the timeline of all comic-book realities, and they theoretically all have access to each other.

?

So for ‘comic-book science’, Hypertime is, if not actually true (remember, I’ve been throwing around metaphors, generalisations, and general fudging left, right and centre here), at least far less ridiculous than it sounds.

But there are some people out there who say that doesn’t actually go far enough – that it’s too conservative a picture of reality. Max Tegmark is one of them.

Tegmark wonders why the set of universes seems to be limited to those that are physically possible – those where the particles are in an arrangement that’s consistent with the laws of physics. He also wonders why it appears possible to describe the laws of physics mathematically, and he’s come to a conclusion that is unprovable – possibly even in theory – but is at the very least interesting.

Tegmark points out that if we can reduce the laws of physics to one equation (as some physicists hope) or a set of equations, then the multiverse described above is the set of all possible solutions to that equation. The multiverse is acting like what in mathematics is called a ‘formal system’ – in fact it *is* a formal system, from the point of view of mathematics (mathematically, if two things behave exactly the same way, they are the same thing) – it’s a set of rules, plus a starting point.

Tegmark wondered why that particular formal system would be the one that would be ‘real’, and he’s been unable to come up with any reason why our one would be ‘real’ but the others wouldn’t. Absent other explanation, he’s decided that our multiverse *isn’t* any more real than the others – that there are as many multiverses out there as there are consistent formal systems. So there’s a multiverse where the laws of physics are the same as our laws of arithmetic, and another one where the laws of physics are the rules of 2D Euclidian geometry. In Tegmark’s neo-Platonic (though he hates the term) view, numbers and triangles aren’t just abstract ideas – they’re things that physically exist, and are precisely as real as you or I.

And so if Tegmark is right, somewhere out there A. Square’s great-great-grandson is busily writing on his blog about these strange, bizarre ideas of Hyperspace that some geometers have been coming up with, where there’s a third spatial dimension…

A brief pop-science bibliography
Here’s a list of books on these subjects that should be comprehensible to people who don’t like looking at equations full of Greek letters. You can’t really grasp this stuff without serious study (and not even then, quite possibly – I’ve read original works by Dirac, Bell, Wheeler, Feynman and so on and still don’t have anything like a proper understanding) but these are all reasonable reads:
The End Of Time by Julian Barbour – a dense read, aimed equally at physicists and a lay audience.
The Fabric Of Reality by David Deutsch – gets far too speculative for my tastes, but a stimlating read.
The Universe Next Door by Marcus Chown – a good summary of the more extravagant ideas at the frontiers of research.
Quantum Reality by Nick Herbert – a very straightforward account of quantum physics.
New Theories Of Everything by John Barrow – a very dense read, on branes, M-Theory and all that stuff.
Programming The Universe by Seth Lloyd – a brief introduction to the field of quantum computing.
Timewarps by John Gribbin – a very 70s book (Gribbin, usually fairly hard-headed, talks here about stuff like past-life regression as a serious possibility) but my first exposure to these ideas. Gribbin’s later In Search Of Schrodinger’s Cat is the ‘canonical’ pop-science book on quantum strangeness.